Shaun, a proposed merge is completed immediately when either of two things happens:
- managers of both profiles approve it
- 30 days have passed, neither manager has rejected it, privacy is open on both, and any member chooses to complete it
If the merge is proposed by a manager of 1 of the profiles, that is deemed to be approval, so when the second manager approves the merge he/she will be the one completing it.
In order to get to complete the merge of a profile you manage, the profile you don't manage needs to be approved before yours!
About the merge order - when the 2 LNABs are identical the merge will AUTOMATICALLY end up with the lower number remaining. It doesn't matter which profile has more or less or better information because all the "free text" content of both will be preserved in the result and it is the responsibility of whoever completes the merge to clean up the biography and sources to effectively merge that into a unified narrative with only a single source list. As to the data, whoever completes the merge will select which profile's data to keep for each item separately.
If the LNABs are not identical (even upper/lower case of the same letter is a difference) then the person proposing the merge has to select the direction and the person completing the merge has an opportunity to change the direction. In this case, it is important to end up with the correct spelling of the LNAB.